.htaccess maker can be used to create .htaccess file out of regular EE template. The .htaccess files can be used to remove index.php from site URLs and to make various types of URL redirects/rewrites - their powers is almost endless.

Now you can use all power of ExpressionEngine templates to create the rules that you want - and no longer need to update files manually.

The .htaccess file will be updated each file a template is created or edited, and also you can invoke update from module's CP.

Create a template that would produce desirable .htaccess (use any EE tags) and provide it in extension settings (as well as path to your .htaccess file) - and you're done!

Below is an example template that makes use of ExpressionEngine query module.
You can have any EE tags in the template, they all will be processed as usually. You can also use special {site_pages} variable, which will return pipe-separated list of all pages created by Pages module.
I suggest to set template type to CSS for better preview

#-------------------start .htaccess-------------------------------------------------
# EE 404 page for missing pages
ErrorDocument 404 /index.php/site/404

# Simple 404 for missing files
<FilesMatch "(\.jpe?g|gif|png|bmp|css|js|flv)$">
  ErrorDocument 404 "File Not Found"
</FilesMatch>

RewriteEngine On
RewriteBase /

# add the www
RewriteCond %{HTTP_HOST} ^domain.com
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=301,L]

# Remove the trailing slash to paths without an extension
RewriteCond %{REQUEST_URI} /$
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)/$ $1 [L,R=301]

######### NOTE:  longer URLs should be listed before the similar shorter ones.

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

# This block is used to let us use different templates for category, subcategory and view page, while URL structure remains the same
# It lets us to now show the actual template used
{exp:query sql="SELECT cat_url_title FROM exp_categories WHERE group_id=3 AND parent_id=0"}
RewriteRule ^about/product/{cat_url_title}(.*)$ /index.php/product/category/{cat_url_title}$1 [L]{/exp:query}
{exp:query sql="SELECT cat_url_title FROM exp_categories WHERE group_id=3 AND parent_id!=0"}
RewriteRule ^about/product/{cat_url_title}/(.+)$ /index.php/product/view/{cat_url_title}/$1 [L]{/exp:query}
{exp:query sql="SELECT cat_url_title FROM exp_categories WHERE group_id=3 AND parent_id!=0"}
RewriteRule ^about/product/{cat_url_title}(.*)$ /index.php/product/subcategory/{cat_url_title}$1 [L]{/exp:query}

RewriteRule ^about/product(.*)$ /index.php/product$1 [L]

{exp:query sql="SELECT cat_url_title FROM exp_categories WHERE group_id=4 AND parent_id=44"}
RewriteRule ^about/{cat_url_title}/(.+)$ /index.php/about/entry/$1 [L]
RewriteRule ^about/{cat_url_title}(.*)$ /index.php/about/list/{cat_url_title}$1 [L]{/exp:query}


# Remove index.php
# Uses the "include method"
# http://expressionengine.com/wiki/Remove_index.php_From_URLs/#Include_List_Method
RewriteCond %{QUERY_STRING} !^(ACT=.*)$ [NC]
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5})$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
# list all template groups
RewriteCond %{REQUEST_URI} ^/({exp:query sql="SELECT group_name FROM exp_template_groups" backspace="1"}{group_name}|{/exp:query}) [NC,OR]
# list all templates in default group (id 1)
RewriteCond %{REQUEST_URI} ^/({exp:query sql="SELECT template_name FROM exp_templates WHERE group_id=1" backspace="1"}{template_name}|{/exp:query}) [NC,OR]
# list all pages
RewriteCond %{REQUEST_URI} ^/({site_pages}) [NC,OR] 
RewriteCond %{REQUEST_URI} ^/(member|P[0-9]{2,8}) [NC]
RewriteRule (.*) /index.php/$1 [L]

#-------------------end .htaccess-------------------------------------------------

Note that the add-on is not yet MSM compatible.